Apparatus for and method of making metallic bellows



sept-,17, 1935. H. A ACEY mmm APPARATUS FOR AND METHOD OF MAKING METALLIC BELLOWS Filed Deo. 24, `1931 QA. Rz

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Patented Sept. 17, 1935 v*UNITED STATES PATENT OFFICE APPARATUS FOR AND METHOD F MAKING METALLIC BELLOWS Harry A. Lacey, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application December 24, 1931,` Serial No'. 583,007

26 Claims. (Cl. 153-71) l ployed for collapsing a blank tube within a die for forming a metallic bellows member. It has been customary to use thin rings cut across their diameter and to space these rings along a die guide preliminary to forming the bellows member. These dies must be individually spaced and clamped and require mechanical means -to insure correct spacing of the convolutions while being collapsed. The die rings are of thin construction and present the problem of a satisfactory bearing therefor. It is necessary in removlng the finished bellows member from the die to unclamp each of the rings or to move the half sections of the die members if rings are not used to release the finished bellows.

It has been diflicult, if not impractical, in previous devices making use of hydraulic pressure and dies for forming metallicY bellows members to provide a constant pressure within the blank tube during the formation of the corrugations on the tube with the result that the hydraulic pressure within the tube would build up and burst the tube during the formation process. This caused a large percentage of rejected tubes which were useless after being formed.

Hence it is an object of my invention to provide an apparatus for making a metallic bellows member which eliminates the undesirable features of the dies now in use.

More specically it is an object of my invention to provide a metallic bellows making apparatus having a one-piece collapsible die which does not have tobe taken down to releas the finished bellows member.

It is another object of my invention to provide an automatic bellows making apparatus in which the internal hydraulic pressure of the tube is maintained constant during the formation of corrugations on the blank tube. Y

Other objects will appear hereinafter.

Briefly, my invention comprises a spiral'resilient die mounted in a pivoted die guide. This die is adapted to receive a blank tube. Mounted above the die for cooperation therewith is a hydraulic device for applying hydraulic pressure Y to the interior of said tube. A ram mounted below the other end of the die is used for collapsing the die and tube while the hydraulic pressure applying device maintains a constant internal pressure within said tube after a predetermined initial pressure has been applied thereto by said hydraulic device.

This hydraulic "device comprises a movable uid cylinder having means for providing a fluidtight connection between the interior of said cylinder and the interior of said tube. A uid operated device moves the cylinder to the position for making the fluid-tight connection which position is maintained by the cylinder during the forming process. A Valve carried by the cylinder is biased to close the passages from the interior of the cylinder to the tube at all times except during the forming process.

Mounted within the cylinder is a piston movable away from and toward the die for forcing fluid from the cylinder into the tube so as to apply an internal pressure thereto. This piston is automatically operated by means of a second fluid-operated device which can exert a predetermined maximum pressurev upon said piston. A valve mounted in the piston closes a passage from a iluid supply to the interior of the cylinder just prior to applying an initial pressure to said tube which pressure is thereafter maintained within the tube while the ram collapses the dieand tube. The operation of the valve within the piston is automatically controlled as the piston moves back and forth within the cylinder during operation of the apparatus. Y

After the die and blank tube have been col- 30 lapsed by the ram the finished bellows is released therefrom by rotating the cylinder thus unscrewing the bellows member. As the cylinder moves away from the die the nished metallic bellows is stripped from the cylinder to which it adheres due to the fluid-tight connection.- formed at the beginning of the process.

For a more complete understanding of my invention reference should be had to the drawing, wherein Fig. 1 shows my apparatus for form- 40 ing Y metallic bellows members with a portion thereof in cross-section to show the internal structure; Fig. 2 is a partial view of my apparatus showing the position of the apparatus upon completion of the collapsing process; Fig. 3 is a View showing another position of a portion of my apparatus prior to stripping of the metallic bellows member; Fig. 4 is a top View of the spiral die and die guide; Fig. 5 is a cross sectionV of the die, die guide, ram and blank tube after initial application of pressure; Fig. 6 shows a cross-section of the die, the blank tube and die guide upon completion of the collapsing process; and Fig. '7 shows the completed metallic bellows.v 55

Referring to the drawing, in Fig. l the base Ill has mounted thereon the supports and I2 which support the platforms I3 and I3', and a pair of brackets I4 and I5 which pivotally support by means of pins I4 and I5 a die guide base I6 to which the die guide I6' is rigidly fastened. The spiral resilient die I1 as shown is provided with a plurality of turns flattened in a direction at right angles to the axis of the die and is attached at one end to a movable ram I8 as at I8 provided with the plunger I9 in contact with the plunger 20 of a hydraulically operated mechanism 2|. The other end of the die is fastened to the upper portion of the die guide I6'. The outer portion of the spiral die is provided with flattened portions parallel with the axis of the tube, the flattened portions serving to support the die in its guide I6 and to limit the axial collapse of the die. Supported at the top of the die guide I6 is a fiuid connection ring 23 which is tapered as at 24, the ring and die receiving the blank tube 22 from which the metallic bellows member is made. Y The hydraulic device for applying the internal hydraulic pressure to the blank tube 22 comprises a movable fluid containing cylinder 26 slidable and rotatable in the bearings 33 and 33' carried by the support 32. At the lower end of the cylinder is a fluid connection plug which cooperates with the ring 23 and has a beveled portion cooperating with the beveled portion 24 of the ring 23. This plug is provided with passages such as 21 for connecting the interior of the cylinder 26 with the interior of the tube 22. A retaining valve 28 is biased by means of spring 25 to close the opening in the fluid connecting plug when the piston 36 slidable in the cylinder 26 is moved to its upper position. This valve carries at the upper end thereof a cup shape member 28 the purpose of which will be described later.

The cylinder 26 is provided with a collar 29 engaged by means of lever 30 pivoted at 30'. The lever 39 is in turn connected to the plunger 13| of the fluid-operated device 32 which in this form of my invention is an air cylinder. When the air cylinder is operated it pivots the lever 30 in a clockwise direction about the pivot 30' to force the cylinder 26 downward and the plug 25 into operative engagement with the blank tube 22 and ring 23 to form a fluid-tight connection between the cylinder 26 and the blank tube 22. This huid-tight connection is maintained throughout the forming process of the tube.

from the die, as will be explained below.

Slidably mounted within the cylinder 26 is a piston 36 which is movable in a Vertical direction with the cylinder. It is provided with an exhaust valve 31 which as shown in the position in Fig. l, is 'biased to its upper position by means of a biasing spring 39. The diameter of the valve is smaller than the diameter of the passageway in the piston in which the valve operates so that when the valve 31 is in its lower position it will open the passage so that the interior of the cylinder 26 is connected to the conduit 38 which is connected to a source of fluid supply not shown.

' With the valve 31 open and the valve 28 7521 open, a direct passage is furnished for liquid from the tube 22 through the cylinder and piston to the source of liquid supply. This opening is for the purpose of permitting excess fluid, for example water, to return to the fluid supply as the piston travels downwardly Within the cylinder prior to applying internal pressure within the tube. This arrangement results in having the same amount of water in the cylinder at the beginning of the formation of the corrugations in the blank at each operation. 10 lfVhen the piston 36 is in its upper position, as shown in Fig. 3, head 40 on the valve 31 engages a stud carried on the support 44 to force the valve downwardly to open the passage to the conduit 38. A spring 42 forces the pin 4| 15 into the groove in the valve stem to maintain the valve open until the piston 36 reaches the position shown in Fig. l at which point the pin 4I is engaged bythe cam 43 to move it to the left so that the biasing spring 39 may again 20 move the Valve to a closed position, the position shown in Fig. 1 being that position just prior to exerting an internal pressure on the blank tube 22.

The operation of the piston 36 is accomplished 25 by means of the hydraulic operating mechanism 49 provided with the plunger 48 and connected to the piston by means of a lever 46 pivoted at 41 on support 44. This operator can exert a given maximum pressure which is used during 30; the formation of the bellows. During the collapsing process hydraulic operator 2| and hydraulic ope-rator 49 oppose each other but the hydraulic operator 2| is capable of exerting a greater pressure than the hydraulic operator 49 35; and hence the operator 49 will move back as the operator 2| moves up, in this manner maintaining a constant predetermined pressure within the blank tube 22 during the forming process.

A stripper 50 is mounted upon the platforms 4.0` I3 and I3 and is for the purpose of stripping the bellows from the plug 25 carried by the cylinder 26 for making the water connection.

Referring to Figs. 2, 3 and 6, it will be observed that a pin I1 inserted in the die guide 45;AA maintains the die in the collapsed position after the bellows member has been formed and after the operator 2| has been deenergized to return its plunger. The motor 34 can then be energized to release the formed bellows from the die by un- 50:; screwing it therefrom.

The operation of my device is as follows: The blank tube 22 is filled with water and placed Within the die I1 and ring 23 carried by the die guide I6 and pivoted to a position below the 55: fluid connecting plug 25 on the cylinder 26. The fluid operated device 32 is energized to move the cylinder 26 down, the plug 25 and the ring 23 cooperating to form the fluid-tight connection by bending the end of the blank tube 22 into the 60a tapered portions of the ring and plug. This fluidtight connection is maintained during the forming process of the metallic bellows member.

The valve 28 during the beginning of the downward movement of the cylinder 26 is in the closed 65v position to retain the uid within the cylinder 26. The piston 36 is in the upper position and the valve 31 is open, as indicated in Fig. 3.

After this fluid-tight connection has been made the hydraulic operator 49 is energized to move 70 downwardly the piston 36 in the cylinder 26. Since the valve 31 is open as the piston moves down the fluid is forced back through the passage around the exhaust valve 31 into the conduit 38 and back to the fluid supply. N

i then'closes the exhaust valve.

w of the turns of the die member.

The piston continues downwardly until it reaches, with respect to the cylinder, the position shown in Fig. 3. Upon continued movement of the piston downwardly the head of the valve 31 passes into the cup 28 carried by the valve 28 and finally the piston engages the cup shaped portion 28 at which time the valve 31 is still in the open position. As the piston moves further the fluid within the cylinder 26 passes around the cup shaped member thro-ugh passages such as 21 Fig. 2, within the cup shaped member past the valve 31 and up through the passage to the conduit 38. Thus the piston, valve 31 and valve 28 begin to move together, and the valve 28 is opened and forced downwardly into the blank tube 22 as shown in Fig. 1. Continued movement of the piston 36 downwardly causes the cam 43 to move the pin 4| so that the exhaust valve 31 is released and the biasing spring It will be apparent then that at this point further movement ofD the piston 36 downwardly will force fluid from the cylinder 26 through the passages 21 into the blank tube 22.

Only a small movementv takes place from the closing of the valve 31 until the piston has reached its lowest position. This small movement however is suicient to increase the internal pressure within the tube so that a bulge -is caused in each portion of the tube between the sections of the spiral guide as shown in Fig. 5. As shown, the die member l1 is formed so that a substantially continuous surface is presented to the tube blank throughout a plurality The internal pressure is thereafter maintained constant during the remainder of the forming process of the tube.

The hydraulic operator 2| is then energized to move the ram I8 up to collapse the die I1 and the tube therein. As it does so fluid is forced from the blank tube into the interior of the cylinder 26, the piston 35 thereafter moving backwardly within the cylinder in response to the pressure exerted thereon by the liquid. The operator 49 being capable of exerting only a predetermined maximum pressure is forced back to its initial position as the ram I Bis moved upwardly. In this way a 'constant pressure is maintained in the tube.

When the die and tube have been completely collapsed, as shown in Fig. 2 and Fig. 6, the retaining valve 28 will have been closed by means of its biasing spring 25', thus breaking the water connection between the interior of the cylinder 23 and the interior of the tube 22. The position of the tube, die, and die guide is shown in the large cross-section in Fig. 6 at this point of the formation of the metallic bellows.

The pin l1 is then moved to engage the ram I8 to maintain the die in the collapsed position and the hydraulic operator 2l is then de-energized permitting plunger 2l) to return to its initial position and the motor 34 energized to rotate the cylinder 25 in its bearings 33 and 33. This causes rotation of the cylinder, the plug 25, and the ring 23 to unscrew the metallic bellows member from the die l1 and move it to the position shown in Fig. 3. As the plunger 3l returns to its initial position the further upward movement of the cylinder 26 causes the ring 23 to come into engagement with the stripper 50 thus releasing the metallic bellows from the plug 25. The metallic bellows member may then be released from the ring 23 manually, the finished product being shown in Fig. 7. As the piston moves upwardly the valve 31 is again reset by the stud 45 to open the passage through the piston to the uid connecting conduit.

By the apparatus and method here disclosed, 5

the complicated and cumbersome dies and die guides heretofore used have been eliminated and a metallic bellows is produced in which, due to the constant internal pressure maintained within the bellows, the walls are maintained practically uniform and in which the percentage of rejection is reduced to a minimum.

While I have described my invention in concrete form and as operating in a specific manner in accordance with the provisions of the patent statutes, it should be understood that I do not limit my invention thereto since various mcdications thereof will suggest themselves to those skilled in the art without departing from the spirit of my invention, the scope of which is set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. An apparatus for making a corrugated tubular member including a spiral die member having a one piece construction throughout the larger portion of at least one turn, said die member being capable of being collapsed in a longitudinal direction, a die guide for supporting said die member and providing for said collapse of said die member, and means for applying an axial pressure to collapse said die member so as to form simultaneously a plurality of corrugations.

2. An apparatus for making a corrugated tubular member from a blanktube comprising a spiral 35 resilient die of one piece adapted to receive a blank tube, a die guide for supporting the same, and means for collapsing the die in a longitudinal direction within said die guide to form corrugations upon said blank tube.

3. The method of producing a corrugated tubular member comprising placing a blank tube within a collapsible die member, applying internal pressure to said tube to produce an initial deformation of said tube to form corrugations thereo-n, compressing said tube and die to form corrugations on said tube, and releasing said compressed tube from the die member by effecting relative rotation between said die member and tube.

4. 'Ihe method of producing a corrugated tubular member comprising placing a blank tube iilled with a liquid within a collapsible die member, connecting said tube with a source of fluid pressure, applying internal pressure to the liquid V in. said tube from said source of fluid pressure to produce an initial deformation of said tube to form corrugations thereon, compressing said tube and die while maintaining the internal pressure of the liquid within said tube constant while forming corrugations on said tube, releasing said tube from said die while said die is in the collapsed position by rotating said tube with respect to said die and stripping said tube from said source of fluid pressure.

5. The method of producing a spiral corrugated tubular member comprising inserting a blank tube in a spiral collapsible die, applying internal pressure thereto for producing an initial deformation of said tube to form corrugations thereon, exerting a longitudinal force on said tube and die for compressing the same to form corrugations thereon while maintaining the internal pressure in said tube constant, and releasing said tube with the corrugations thereon from said die while said die is in the collapsed position by rotating said tube with respect to said die.

6. An apparatus for making a corrugated tubular member including a resilient spiral die adapted to receive a blank tube, a die guide for supporting said die and tube, means including a movable fluid containing cylinder adapted to have a huid-tight engagement with said tube, a piston in said tube for forcing fluid from said cylinder into said tube for exerting an internal pressure within said tube for forcing said tube between the coils of said spiral die, means for moving said cylinder into engagement with said tube,

other means for moving said piston, and means for collapsing the die and tube in a longitudinal direction for forming corrugations upon said tube, said piston moving in said cylinder to automatically maintain a constant internal pressure during said collapsing process.

7. An apparatus for making a corrugated tubular member including a one piece spiral resilient die adapted to receive a blank tube, a die guide for holding said die during the corrugation form- :ing operation, means for exerting an internal pressure within said tube and a ram movable within said guide to collapse said tube and die While said internal pressure is maintained constant.

8. An apparatus for making a corrugated tubular member comprising a collapsible forming member into which a blank tube may be placed, means including a movable uid cylinder having a passage to the interior thereof, means carried thereby for automatically forming a fluid-tight connection` with said tube when said cylinder is moved to engage said tube, a valve carried by said cylinder for closing the opening thereto, means carried by said cylinder for applying internal pressure to said tube to produce initial deformation in the side of said tube, said valve automatically opening to connect the interior of said cylinder and said tube when said pressure-supplying means is operated, and means for thereafter collapsing said forming member and tube to produce corrugations on said tube, said internal pressure applying means maintaining a constant pressure in said tube during said collapsing process.

9. An apparatus for making a corrugated tubular member comprising a one piece collapsible die adapted to receive a blank tube, means for applying an internal pressure to said tube to produce initial deformations in the sides thereof to start the corrugations, a device engaging said die and tube for collapsing the saine whereby corrugations are produced on said tube by said collapsible die, said internal pressure applying means automatically maintaining a constant internal pressure in said tube while said tube and die are being collapsed, and means for releasing said tube from said die after said die and tube have been collapsed.

10. An apparatus for making a corrugated tubular member comprising a collapsible forming die adapted to receive a blank tube, hydraulic means including a movable fluid-containing cylinder and a piston therein for applying an internal pressure to said tube, means carried by said cylinder for automatically forming a Huid-tight connection between said tube and said cylinder when said cylinder is moved to engage said tube, means for moving said piston to apply pressure within said tube to provide an initial bulge therein, and a movable ram engaging said collapsible die and tube for collapsing said tube and die to protubular member comprising a collapsible helical 5 die adapted to receive a blank tube, hydraulic means including a rotatable fluid containing cylinder for applying an internal pressure tosaid tube, and means associated with said die and said cylinder to provide a fluid-tight connection between said hydraulic pressure applying means and said tube, a ram for collapsing said tube and said die to produce corrugations on said tube, means for automatically maintaining a constant internal pressure in said tube while said ram collapses said die and tube, and means for rotating said cylinder to release said tube from said die.

12. An apparatus for making a corrugated tubular member comprising a collapsible spiral forming die adapted to' receive a blank tube, an 20 hydraulic device including a movable uid-containing cylinder for applying internal pressure to said tube to force said tube against said forming die, means carried by said cylinder for cooperating with said die for automatically forming a fluid-tight connection between said tube and said hydraulic device when said cylinder is moved to engage said tube, means for operating said hydraulic device to produce an initial pressure within said tube to start the formation of corrugations thereon, a ram cooperating with said die and said tube for collapsing said die and said tube to form the corrugations on said tube, said hydraulic operating device automatically maintaining a constant internal pressure in said tube as said tube is being collapsed.

13. An apparatus for making a corrugated tubular member comprising a collapsible spiral forming die adapted to receive a blank tube, a movable die guide for holding said die whereby said die and guide can be moved from a tube receiving position to a corrugation forming position, an hydraulic device for applying internal pressure to said tube to force said tube against said forming die, means carried by said hydraulic device and cooperating with said die for forming a fluid-tight connection between said tube and said hydraulic device, means for operating said hydraulic device to produce an initial pressure within said tube to start the formation of corrugatio-ns thereon, a ram carried by said die guide and cooperating with said die and said tube for collapsing said die and said tube to form the corrugations on said tube, said hydraulic operating device automatically maintaining a constant internal pressure in said tube as said tube is being collapsed, and means for releasing said tube from said die after said tube and die have been collapsed.

14. An apparatus for making a corrugated tubular member comprising a collapsible spiral forming die adapted to receive a blank tube, an hydraulic device for applying internal pressure to said tube to force said tube against said forming die, means carried by said hydraulic device and cooperating with said die for forming a fluidtight connection between said tube and said hydraulic device, means for operating said hydraulic device to produce an initial pressure within said tube to start the formation of corrugations thereon, a ram cooperating with said die and said tube for collapsing said die and said tube to form the corrugations on said tube, said hydraulic operating means automatically maintaining a constant internal pressure in said tube as said tube is V2,014,972 -being collapsed, means for rotating said tube with respect to said die for releasing said tube from said die after said tube and die have been collapsed, and means for releasing said formed tube from said fluid-tight connecting means.

Y l5. An apparatus for making a corrugated tubular member comprising a collapsible die adapted to receive a blank tube, a hydraulic device co-mprising a fluid cylinder provided with means for forming a fluid-,tight connection with said blank tube, a valve controlling the flo-w of fluid between said cylinder and said tube, and a piston in said cylinder operable to increase the pressure within said tube to a predetermined value, means for operating said piston, means cooperating with said die and tube for collapsing said die and tube to form corrugations on said tube, said piston being automatically movable to maintain the internal pressure within said tube constant as said tube is being collapsed.

16. An apparatus for making a corrugated tubular member comprising a die member adapted to receive a blank tube, a hydraulic device comprising a fluid cylinder provided with means for forming a fluid-tight connection with said blank, communicating passages in said fluid connecting means for connecting the interior of said cylinder with said tube to permit iiuid to pass between said cylinder and said tube, a retaining valve biased to close said passages, means for operating said cylinder to make said iiuid connection, a piston within said cylinder having passages communicating with the interior of said cylinder and with a source of fluid supply, an exhaust valve biased to close said passage and an operating device for moving said piston within said cylinder to force fluid from said cylinder to said tube when said exhaust valve is in the closed position, and a ram cooperating with said tube and die for collapsing the same to form corrugations thereon, said piston being movable in said cylinder to automatically maintain a constant pressure in said tube as said tube is collapsed.

17. An apparatus for making a corrugated tubular member comprising a forming die adapted to receive a blank tube, an hydraulic pressure applying means for applyinginternal pressure to said blank tube comprising a movable cylinder and piston, said cylinder and piston havingy relative movement with respect to each other, means on said cylinder for providing a fluid-tight connection with said tube, means for operating said cylinder to a position to form said fluid-tight connection, passageways in said connecting means for connecting the interior of said tube and interior of said cylinder whereby fluid may -pass between said cylinder and said tube, means for moving said piston in said cylinder to force liquid from said cylinder into said tube for producing an internal pressure therein of predetermined value, and means for collapsing said tube and die to form corrugations on said tube, said piston moving to automatically maintain a constant pressure within said tube.

18. An apparatus for making a corrugated tubular member comprising a forming die adapted to receive a blank tube, an hydraulic pressure applying means for applying internal pressure to said blank tube comprising a movable cylinder and piston, said cylinder and piston having relative movement with respect to each other, means on said cylinder for providing a fluidtight connection with said tube, means for operating said cylinder to a position to form said huid-tight connection, passageways in said connecting means for connecting the interior of said tube and interior of said cylinder whereby iiuid may pass between said cylinder and said tube, means for moving said piston in said cylinder to force liquid from said cylinder into said tube for producing an internal pressure therein of predetermined value, means for collapsing said tube and die to form corrugations on said tube, said piston moving to automatically maintain a constant pressure within said tube, and means for releasing -said formed tube from said die.

19. An apparatus for making a corrugated tubular member comprising a helical collapsible die for receiving a blank tube, a pivoted die guide for supporting the same, an hydraulic device for applying an internal hydraulic pressure to said tube comprising a movable cylinder having a fluid therein, a connecting means for forming a fluid-tight connection between said cylinder and said tube including a plug mounted on said cylinder and a cooperating ring carried by said die guide, means for moving said cylinder to move said plug against said ring to form a uid-tight connection, said plug being provided with passages therethrough for connecting the interior of said cylinder and said tube, a valve biased to close said passages, a piston within said cylinder having passages for connecting the interior of said cylinder with a source of fluid supply, a valve biased to close said passages, means for operating said last named valve to open position when said piston is moved away from said plug, and means for maintaining said last named valve open, said piston when operated toward said plug contacting with said iirst named valve to open the passageways in said plug whereby a passageway from the interior of said blank tube to said source of fluid supply is provided, means for closing said last named valve when said piston approaches said plug, movement of the piston toward said plug thereafter increasing the pressure within said plug to a predetermined value, and other means for collapsing said die and tube to form corrugations thereon, said piston moving away from said plug to maintain the pressure within said tube constant while it is being collapsed.

20. An apparatus for making a corrugated tubular member including an hydraulic pressure applying means comprising a movable cylinder, a plug, an opening in said plug and passages connecting said opening and the interior of said cylinder, a valve biased to close said opening, and a piston in said cylinder movable to open said valve and force iiuid through said passageways and opening.

21. An apparatus for making a corrugated tubular member including an hydraulic pressure applying means comprising a movable cylinder, a plug, an opening in said plug, and passageways connecting said opening and the interior of said cylinder, a retaining valve biased to close said opening, a piston in said cylinder movable to open said valve and force fluid through said passageways and opening, said piston having a passage therein connecting the cylinder and a source of fluid supply and an exhaust valve carried by said piston for closing the passage in said piston said valve being open during a portion of the movement of said piston to permit liquid to pass through said passage to and trom the interior of said cylinder and means for closing said eX- haust valve at a predetermined point of travel of said piston in opening said retaining valve whereby said liquid may be forced under pressure through said passageways and opening in said plug.

22. An apparatus for making a corrugated tubular member comprising a collapsible spiral forming die adapted to receive a blank tube, a hydraulic device for applying internal pressure to said tube including a rotatable fluid-containing cylinder, means carried by said cylinder for providing a fluid-tight connection between said cylinder and said tube, a piston movable in said cylinder for forcing iiuid from said cylinder into said tube for applying a pressure thereto to force said tube against said forming die after said uid connection is made, means for collapsing said die and tube to form corrugations thereon, said piston automatically receding within said cylinder to maintain the pressure within said tube constant during said collapsing process, means rotating said cylinder to release said tube from said die after said tube has been collapsed, and means for cooperating with said cylinder for stripping said tube from said fluid-connecting means.

23. An apparatus for making a corrugated tubular member including a collapsible die for receiving a blank tube, means for applying an internal pressure to said tube including a movable piston, means carried by said piston for automatically forming a fluid-tight connection between said tube and said cylinder, means for moving said cylinder to engage said tube and said connecting means, a piston within said cylinder, means for moving said piston Within said cylinder after said fluid-tight connection has been made to apply an internal pressure to said tube to force said tube against said forming die, means for collapsing said die and tube to form corrugations on said tube, said piston moving within said cylinder to maintain the pressure in said tube constant during collapsing thereof, means for releasing said tube from said die, and

other means for stripping said tube from said connecting means.

24. An apparatus for making a corrugated tubular member including a substantially spiral die member provided with a plurality of turns flattened in a direction at right angles to the axis of said die member and adapted to receive a blank tube, a die guide for supporting said plurality of turns of said die member, and means for applying a radial pressure over the surface of said blank tube adjacent said die member to form simultaneously corrugations between said turns of said die member.

25. An apparatus for making a corrugated tubular member including a one-piece substantially spiral resilient die having a plurality of turns adapted to receive a blank tube, said turns of said die being flattened in a direction at right angles to the axis of said die, a die guide for supporting said plurality of turns of said die, and means for collapsing said die to produce simultaneously corrugations throughout the length of said tubular member.

26. An apparatus for making a corrugated tubular member including a resilient substantially spiral die member adapted to receive a blank tube, said die member being provided with a plurality of turns flattened in a direction at right angles to the axis of said die, a die guide for supporting said die member and tube, said turns of said die member being provided with flattened portions parallel with the axis of said tube for supporting said die member against said guide, means for introducing iiuid under pressure to said tube to expand said tube between the turns of said die member, and means for collapsing said die member in a longitudinal direction to form corrugations upon said tube, said fiattened portions of said turns cooperating with each other to limit the axial collapse of said tube.

HARRY A. LACEY. 

